This invention relates to fluid flowmeters, and, more particularly, to an improved fluid flowmeter transducer device specially suited for use in engine fuel consumption and/or management systems for combustion powered engines.
An example of a fuel metering system in which the herein described flowmeters may be employed is illustrated by U.S. Pat. No. 4,048,964, which requires a fuel flowmeter transducer device developing a pulsatory electrical signal whose pulse repetition rate varies linearly in accordance with the flow rate of fuel supplied to the engine. Air supplied to the engine is sensed by a swirl-type air flowmeter whose pulsatory electrical signal output is processed together with the fuel signal pulses from the fuel flowmeter by a mass fuel/air ratio scheduled electronic controller, which controls a fuel metering or supply device to supply fuel to the engine precisely in accordance with the scheduled fuel/air ratio.
The abovementioned fuel metering system is intended to meet stringent engine emission and fuel economy mandates for production vehicles and requires, for its successful implementation, precise and reliable instruments possessed of a high degree of accuracy and linearity over the entire range of engine performance and vehicle operating conditions. In addition to a low pressure drop, the fuel flowmeter or flow transducer device should produce a high pulse count output at low fuel flow rates, as during engine idle conditions, and should also exhibit a fast response to fluid flow rate changes as well as a rapid run-down or braking characteristic when the fluid flow therethrough has been decreased, as during vehicle deceleration conditions. Consistent and optimum performance and repeatability of results between production flowmeters are also necessary criteria.
Known forms of prior art flowmeters, as exemplified by U.S. Pat. Nos. 3,392,021; 3,867,840; and 4,047,433, for example, fall short of meeting the foregoing requirements.
The present invention thus seeks generally and has among its objects to provide a fuel flowmeter transducer device possessed of the above enumerated and other desirable characteristics and which is of compact size, composed of a minimum number of parts and is of simple and inexpensive construction suited to high volume production fabrication.